More than 80% of retiring firefighters are now obtaining lucrative disability pensions.

An astounding 80 percent of firefighters and chiefs who have retired so far this year were given exorbitant disability pensions, further crippling the city’s worst-funded retirement system.

A year after The Post exposed a sky-high 70 percent disability-pension rate for FDNY retirees, the latest rate skyrocketed, with 105 out of 132 total retirees approved for the generous payouts.

Since 2008, 86 percent of new FDNY retirees got disability pensions, up from about 65 percent in the six prior years.

The disability bonanza has swelled the cost of the taxpayer-funded pensions to nearly $1 billion a year. According to the city’s latest financial report, the city’s five pension funds are short nearly $40 billion on their future obligations.

After working 20 years, firefighters and other FDNY staffers can start collecting a regular pension of 50 percent of their final year’s pay, or the average of their last three years, including overtime. The pension is exempt from city and state income tax, but not federal.

But those with disability retirements receive three-quarters of their final pay, almost completely tax free.

A Post review found:

* Nearly nine out of 10 of the FDNY’s 963 retirees since 2008 are collecting a disability pension.

* The average annual pension for new retirees is nearing $100,000 — up from about $50,000 20 years ago — and typically pays more than $2 million over a retiree’s remaining life span.

* Close to half of the 2,093 disability pensions granted from 2004 to 2008 were approved under “presumptive bills” — pension laws that automatically presume any city firefighter’s or supervisor’s cancer, or heart or lung problems, are job-related, ignoring other possible causes such as smoking or obesity.

* Scores of firefighters who previously retired with regular service pensions are now applying and being approved for even more costly World Trade Center disability pensions, which cover family members even after the retiree’s death.

* Some questionable applications are emerging, including an FDNY doctor who never battled a blaze in line for a $95,000-a-year “heart bill” pension, as The Post reported last week.

According to the city’s latest annual financial report, New York City’s five pension funds, including those for teachers, police officers and firefighters, are short nearly $40 billion on their future obligations. The taxpayer tab for these pensions is expected to grow to $12.3 billion per year by 2016.

The FDNY’s pension fund has the biggest shortfall because of the surging number of disability pensions and collapsing investment returns. The system is only 55 percent funded, with more than $5 billion in uncovered obligations, the city’s Comprehensive Annual Financial Report shows.

Al Hagen, president of the Uniformed Fire Officers Association, defended the current setup, saying his members are sicker than ever.

“Firefighting is an extraordinarily dangerous job,” he said. “We only hope that our members who retired under the disability live long enough to enjoy those pensions.”